A.R.
K., Both of my sons had strong separation anxiety. I am not sure you need to read anymore because you know the basics. I am a child development specialist and separation anxiety is a normal step in a child's emotional development. It means he is attached to you and that is a good thing. Please do not let people convince you that it is worse because you stay at home. NOT TRUE. Children experience it in different degrees and in my experience boys usually (not always) have it worse. I think that is partly because they are usually developmentally less mature. Also they do not tend to have the level of social skills that girls have.
Could you trade time with a mom who has a child and is at home? If it is someone he knows and there are not a lot of other kids to be with it may be less threatening and he can get the emotional attention he needs to cope. It would be great if you had a friend who would bring their child to your home and you leave. That way he is in a familiar surrounding. Then you take a turn with the other mom.
You need to get out. I remember that but if you picture your child crying the entire time it isn't relaxing. Just try small amounts at first. Maybe only do one day if you use the day care center. He will come around. Slow and steady wins the race.
I'd love to hear how it goes if you want to write. I really struggled with this with my sons. A.